Adaptive impedance matching apparatus,system and method with improved dynamic range

ABSTRACT

An embodiment of the present invention provides an apparatus, comprising an RF matching network connected to at least one RF input port and at least one RF output port and including one or more voltage or current controlled variable reactive elements; a voltage detector connected to the at least one RF output port via a variable voltage divider to determine the voltage at the at least one RF output port and provide voltage information to a controller that controls a bias driving circuit which provides voltage or current bias to the RF matching network; a variable voltage divider connected to the voltage detector and implemented using a multi-pole RF switch to select one of a plurality of different resistance ratios to improve the dynamic range of the apparatus; and wherein the RF matching network is adapted to maximize RF power transferred from the at least one RF input port to the at least one RF output port by varying the voltage or current to the voltage or current controlled variable reactive elements to maximize the RF voltage at the at least one RF output port.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/594,309, filed Nov. 8, 2006, entitled, ADAPTIVE IMPEDANCE MATCHINGAPPARATUS, SYSTEM AND METHOD WITH IMPROVED DYNAMIC RANGE, by William E.McKinzie.

BACKGROUND

The function of an adaptive impedance matching module is to adaptivelymaximize the RF power transfer from its input port to an arbitrary loadimpedance ZL that changes as a function of time.

One of the important engineering specifications of an impedance matchingcontrol system is the dynamic range of input power over which it willoperate. The lowest cost RF voltage detector is a simple diode detector,but it has a limited dynamic range of about 25 dB. Logarithmicamplifiers (that detect the signal envelope) have a much higher dynamicrange of 50 dB to 60 dB, but their cost, complexity, chip area, andcurrent drain is also much higher. Thus, a strong need exists for animproved adaptive impedance matching apparatus, system and method.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides an apparatus, comprisingan RF matching network connected to at least one RF input port and atleast one RF output port and including one or more voltage or currentcontrolled variable reactive elements, a voltage detector connected tothe at least one RF output port via a variable voltage divider todetermine the voltage at the at least one RF output port and providevoltage information to a controller that controls a bias driving circuitwhich provides bias voltage or bias current to the RF matching network,and wherein the RF matching network is adapted to maximize RF powertransferred from the at least one RF input port to the at least one RFoutput port by varying the voltage or current to the voltage or currentcontrolled variable reactive elements to maximize the RF voltage at theat least one RF output port.

In an embodiment of the present invention, the voltage detector may be adiode detector and wherein the variable voltage divider connected to thevoltage detector may be adapted to improve the dynamic range of theapparatus. Further, a loop controller may be associated with thevariable voltage divider to make the variable voltage dividerprogrammable and the variable voltage divider may be implemented using amulti-pole RF switch to select one of a plurality of differentresistances. In an embodiment of the present invention, the variablevoltage divider may be operable to allow a detector coupled to theoutput port to be more isolated at higher power levels and improvelinearity of the module for high signal levels. Further, the RF outputnode may be connected to a shunt RF branch comprising a series string ofcapacitors and by selectively tapping into various circuit nodes alongthe string, a variable output voltage divider is obtained. In anembodiment of the present invention and not limited in this respect,tapping into various circuit nodes may be accomplished using a digitallycontrolled RF switch and the RF switch may be selected from the groupconsisting of: FETs, MEMS or PIN diodes.

In yet another embodiment of the present invention is provided a methodof adaptive impedance matching, comprising connecting an RF matchingnetwork to at least one RF input port and at least one RF output portand including one or more voltage or current controlled variablereactive elements, using a voltage detector connected to the at leastone RF output port via a variable voltage divider to determine thevoltage at the at least one RF output port and providing the voltageinformation to a controller that controls a bias driving circuit whichprovides bias voltage or bias current to the RF matching network, andadapting the RF matching network to maximize RF power transferred fromthe at least one RF input port to the at least one RF output port byvarying the voltage or current to the voltage or current controlledvariable reactive elements to maximize the RF voltage at the at leastone RF output port.

In still another embodiment of the present invention is provided amachine-accessible medium that provides instructions, which whenaccessed, cause a machine to perform operations comprising connecting anRF matching network to at least one RF input port and at least one RFoutput port and including one or more voltage or current controlledvariable reactive elements, using a voltage detector connected to the atleast one RF output port via a variable voltage divider to determine thevoltage at the at least one RF output port and providing the voltageinformation to a controller that controls a bias driving circuit whichprovides voltage or current bias to the RF matching network, andadapting the RF matching network to maximize RF power transferred fromthe at least one RF input port to the at least one RF output port byvarying the voltage or current to the voltage or current controlledvariable reactive elements to maximize the RF voltage at the at leastone RF output port.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

FIG. 1 illustrates a block diagram of an adaptive impedance matchingmodule AIMM control system of one embodiment of the present invention;

FIG. 2 illustrates a control system for a multi-port adaptive impedancematching module of one embodiment of the present invention;

FIG. 3 shows an implementation of an AIMM closed loop control system ofone embodiment of the present invention;

FIG. 4 is a block diagram of an adaptive impedance matching module(AIMM) with a variable voltage divider for improved dynamic range of oneembodiment of the present invention;

FIG. 5 illustrates an embodiment of an enhanced dynamic range AIMMcontrol system; and

FIG. 6 shows a second embodiment of an enhanced dynamic range AIMMcontrol system.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, components and circuitshave not been described in detail so as not to obscure the presentinvention.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations may be the techniques usedby those skilled in the data processing arts to convey the substance oftheir work to others skilled in the art.

An algorithm is here, and generally, considered to be a self-consistentsequence of acts or operations leading to a desired result. Theseinclude physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers or the like.It should be understood, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices.

Embodiments of the present invention may include apparatuses forperforming the operations herein. An apparatus may be speciallyconstructed for the desired purposes, or it may comprise a generalpurpose computing device selectively activated or reconfigured by aprogram stored in the device. Such a program may be stored on a storagemedium, such as, but not limited to, any type of disk including floppydisks, optical disks, compact disc read only memories (CD-ROMs),magnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), electrically programmable read-only memories (EPROMs),electrically erasable and programmable read only memories (EEPROMs),magnetic or optical cards, or any other type of media suitable forstoring electronic instructions, and capable of being coupled to asystem bus for a computing device.

The processes and displays presented herein are not inherently relatedto any particular computing device or other apparatus. Various generalpurpose systems may be used with programs in accordance with theteachings herein, or it may prove convenient to construct a morespecialized apparatus to perform the desired method. The desiredstructure for a variety of these systems will appear from thedescription below. In addition, embodiments of the present invention arenot described with reference to any particular programming language. Itwill be appreciated that a variety of programming languages may be usedto implement the teachings of the invention as described herein. Inaddition, it should be understood that operations, capabilities, andfeatures described herein may be implemented with any combination ofhardware (discrete or integrated circuits) and software.

Use of the terms “coupled” and “connected”, along with theirderivatives, may be used. It should be understood that these terms arenot intended as synonyms for each other. Rather, in particularembodiments, “connected” may be used to indicate that two or moreelements are in direct physical or electrical contact with each other.“Coupled” my be used to indicated that two or more elements are ineither direct or indirect (with other intervening elements between them)physical or electrical contact with each other, and/or that the two ormore elements co-operate or interact with each other (e.g. as in a causean effect relationship).

An embodiment of the present invention provides closed-loop control ofan adaptive impedance matching module (AIMM). The RF output node voltageof the AIMM tuner circuit may be monitored and maximized to insure thebest available impedance match to arbitrary load impedance. In addition,improvement in dynamic range may be achieved by adaptively changing theRF coupling level between the voltage sensed at the output port (antennaside) of the matching network and the voltage provided to the detector.This coupling level may be controlled by a processor which also does theclosed loop tuning. A simple voltage divider comprised of resistors anda digitally controlled RF switch may be used to realize variablecoupling levels, although the present invention is not limited in thisrespect. Another means of realizing variable coupling levels is todigitally switch between different tap points in a series string ofvariables capacitors which form a shunt voltage tunable dielectriccapacitor at the output node of the AIMM tuner.

The function of an adaptive impedance matching module (AIMM) is toadaptively maximize the RF power transfer from its input port to anarbitrary load impedance Z_(L) where the load changes as a function oftime. Turning now to the figures, FIG. 1, shown generally as 100, is anAIMM block diagram.

The RF matching network 110 may contain inductors and capacitorsrequired to transform the arbitrary load impedance Z_(L) 135 to animpedance equal to or close to a defined system impedance, such as 50ohms. The net benefit of this transformation is an improvement in thelevel of power transferred to the load Z_(L) 135, and a reduction in thelevel of reflected power from the RF input port 105. This second benefitis also known as an improvement in the input mismatch loss wheremismatch loss is defined as (1−|S₁₁|²).

The RF matching network 110 may contain one or more variable reactiveelements which are voltage controlled. The variable reactive elementsmay be, although are not required to be, variable capacitances, variableinductances, or both. In general, the variable capacitors may besemiconductor varactors, MEMS varactors, MEMS switched capacitors,ferroelectric capacitors, or any other technology that implements avariable capacitance. The variable inductors may be switched inductorsusing various types of RF switches including MEMS-based switches. Thereactive elements may be current controlled rather than voltagecontrolled without departing from the spirit and scope of the presentinvention.

In an embodiment of the present invention, the variable capacitors ofthe RF matching network may be tunable integrated circuits, such asvoltage tunable dielectric capacitors or Parascan Tunable Capacitors(PTCs). Each tunable capacitor may be realized as a series network ofcapacitors which are all tuned using a common tuning voltage.

The RF voltage detector 130 of FIG. 1 may be used to monitor themagnitude of the output nodal voltage. The fundamental concept used inthis control system is that the RF power transferred to the arbitraryload impedance 135 is maximized when the RF voltage magnitude at theoutput port 115 is maximized. It is the understanding of this conceptthat allows one to remove the directional coupler conventionally locatedin series with the input port and to thus simplifying the architectureof the control system. A directional coupler is undesirable for numerousreasons:

-   -   (1) The cost of the coupler,    -   (2) The physical size of the directional coupler may be        prohibitive: Broadband couplers are typically ¼ of a guide        wavelength in total transmission line length at their mid-band        frequency. For a 900 MHz band and an effective dielectric        constant of 4, the total line length needs to be about 1.64        inches.    -   (3) The directivity of the directional coupler sets the lower        limit on the achievable input return loss of the RF matching        network. For instance, a directional coupler with 20 db of        coupling will limit the input return loss for the AIMM to about        −20 dB.    -   (4) Directional couplers have limited operational bandwidth,        where the directivity meets a certain specification. In some        applications, the AIMM may need to work at different frequency        bands separated by an octave or more, such as at 900 MHz and        1900 MHz in a commercial mobile phone.

The RF voltage detector 130 may be comprised of a diode detector, atemperature compensated diode detector, a logarithmic amplifier, or anyother means to detect an RF voltage magnitude. The phase of the RFvoltage is not required. The controller 125 accepts as an input theinformation associated with the detected RF output 115 voltage. Thecontroller 125 provides one or more outputs that control the biasvoltage driver circuits. The controller 125 may be digitally-based suchas a microprocessor, a digital signal processor, or an ASIC, or anyother digital state machine. The controller may also be an analog-basedsystem.

The bias voltage driver circuit 120 is a means of mapping controlsignals that are output from the controller 125 to a voltage range thatis compatible with the tunable reactive elements in the RF matchingnetwork 110. The driver circuit may be an application specificintegrated circuit (ASIC) whose function is to accept digital signalsfrom the controller 125 and then output one or more analog voltages forone or more tunable reactive elements in the RF matching circuit 110.The driver circuit 120 may provide a wider range of analog tuningvoltages than what is used as a power supply voltage by the controller125. Hence the driver circuit 120 may perform the functions of voltagetranslation and voltage scaling.

The purpose of the control system shown in FIG. 1 is to monitor theoutput RF voltage magnitude and to use this information as an input toan algorithm that adjusts the tuning voltages provided to the tunablereactive elements in the RF matching network 110. The algorithm adjuststhe reactances to maximize the RF output 115 voltage. Various optionsexist for control algorithms. In general, the algorithm may be a scalarmulti-dimensional maximization algorithm where the independent variablesare the tuning voltages for the reactive elements. Some embodiments ofthe operation of the tuning algorithm of the present invention, mayincrease performance of a network and/or enable it to perform in systemsthat might otherwise make it difficult for the system to make all therequired system specifications. GSM, EDGE and WCDMA systems havespecification limiting the allowable phase shifts within a transmitburst. Additionally, all cellular handsets have SAR (specific absorptionrate) limits dictating how much RF energy may be absorbed by humanbodies in close proximity. There are soon to be specifications that willdictate TRP (total radiated power) to be transmitted by cellularhandsets, and handset suppliers will need to meet these specificationswithin a small number of transmit bursts (in a TDMA system) or in a veryshort period of time (in a continuous transmission system).

In order to achieve the above objectives, the AIMM tuning algorithm cancontain the following attributes: 1—Limit the number of tuning “steps”that are taken within a transmit burst, or limit the steps to only beallowed between bursts (when the transmitter is disabled). This can beaccomplished easily by putting time delays in the algorithm, or to onlyallow tuning when a Tx Enable line in the transmitter is low.2—Limit the allowed tuning to avoid certain matching impedances, or putthe tuner in a “default” position when the cellular handset transmitteris at the full power step. By doing so at the highest power level, wecan avoid having the handset antenna couple higher power into the humantissue near the phone's antenna. It is only at the highest power levelwhere the SAR limit typically becomes an issue, and by limiting theeffectiveness of the AIMM tuner at this power level, we can avoid thepossibility of causing the handset to exceed the SAR limits.3—In order to allow the AIMM tuner to achieve the optimal match asquickly as possible, a memory system could be engaged in which theoptimal match is stored for each frequency band, or perhaps even foreach group of channels, and this memorized optimal match is used as thestarting position any time the phone is directed to that particular bandor channel. This memory could also remember operating positions such asflip-open or flip-closed in order to better “guess” the best startingposition for the matching network.

The simplified control system shown in FIG. 1 is illustrated using a 2port RF matching network. However, this control system is extensible tomulti-port RF matching networks as shown in FIG. 2, generally as 200.Consider a RF multiplexing filter with N input ports where each port isdesigned for a specific band of frequencies. Assume that N transmittersdrive the N input ports 205, 210, 215 and 220, and that each input portis coupled to the single RF output port 240 using RF circuits thatcontain variable reactive elements. The objective of the control systemremains the same, to maximize the RF output voltage magnitude, and thusto optimize the power transfer from the nth input port to the arbitraryload impedance. Further, the RF voltage detector 245, controller 235 andbias voltage driver circuit 230 functions as described above withreference to FIG. 1 and in the embodiment of FIG. 2, the RF matchingnetworks is a multi-port RF matching network 225.

Although the present invention is not limited in this respect, thearbitrary load impedance Z_(L) 250 may be a multi-band antenna in amobile wireless device and the multi-port matching network 225 may be adiplexer whose function is to route the signal between two or more pathsby virtue of the signal frequency.

Looking now at FIG. 3, the variable capacitors (such as, but not limitedto, PTCs) 320, 325 and 330 and inductors 305 and 310 may be built into amultichip module 300 containing a detector 360, an ADC 365, a processor355, DACs 370, voltage buffers, and charge pump 335. This multichipmodule 300 may be designed with a closed loop feedback system tomaximize the RF voltage across the output node by adjusting all the PTC320, 325 and 330 bias voltages, and doing so independently.

In an embodiment of the present invention as provided in FIG. 3, the RFmatching network may be comprised of inductors L₁ 310, L₂ 305 andvariable capacitors PTC₁ 320, PTC₂ 325 and PTC₃ 330. Note that eachvariable capacitor may itself be a complex network. The RF voltagedetector 360 in this AIMM may be comprised of a resistive voltagedivider (5KΩ/50Ω) and the simple diode detector. In an embodiment of thepresent invention, the controller may be comprised of theanalog-to-digital converter or ADC₁ 355, the microprocessor 355, plusthe digital-to-analog converters DAC₁ 370, DAC₂ 375 and DAC₃ 380. Thecontroller may use external signals such as knowledge of frequency, Txor Rx mode, or other available signals in the operation of its controlalgorithm. The bias voltage driver circuit may be comprised of aDC-to-DC converter such as the charge pump 335, in addition to the threeanalog buffers whose output voltage is labeled V_(bias1), 385, V_(bias)390, and V_(bias3) 395. The DC-to-DC voltage converter may be needed tosupply a higher bias voltage from the analog buffers than what isnormally required to power the processor 355. The charge pump may supplya voltage in the range of 10 volts to 50 volts, and in some embodiments,both positive and negative supply voltages may be used.

It should be noted that the RF matching network shown in FIG. 2 isrepresentative of many possible circuit topologies. Shown in FIG. 2 is aladder network, but other topologies such as a T or Pi network may beused. The variable reactive elements (capacitors) are shown in shuntconnections but that is not a restriction, as they may be used in seriesin other applications. Furthermore, three independent variablecapacitances are shown in this RF matching network. However, fewer ormore variable reactive elements may be used depending on the complexityneeded to meet RF specifications.

In FIG. 3, the inductors for the RF matching network are shown to beincluded in the AIMM multichip module. In practice, this may not alwaysbe the case. If the module is extremely small, it may be more convenientto use external inductors for the matching network. External inductorsmay have a higher Q factor than smaller inductors that are able to beintegrated on the module.

One of the important engineering specifications of the simplified AIMMcontrol system is the dynamic range of input power over which it willoperate. The lowest cost RF voltage detector is a simple diode detector,but it has a limited dynamic range of about 25 dB. Logarithmicamplifiers (that detect the signal envelope) have a much higher dynamicrange of 50 dB to 60 dB, but their cost, complexity, chip area, andcurrent drain is also much higher. In an embodiment of the presentinvention, as illustrated in FIG. 4 at 400, one may use a variablevoltage divider to improve the dynamic range of a simple diode detector.The variable voltage divider 430 may be added between the RF output port435 and the RF voltage detector 425. It is controlled by the loopcontroller 420 (microprocessor, ASIC, etc), and therefore it is aprogrammable voltage divider. Bias voltage driver circuit 415 and RFmatching network 410 operate as described above with respect to FIG. 1.

As shown in FIG. 5, an embodiment of the present invention provides asimple resistive voltage divider 550 which is implemented using athree-pole RF switch 560 to select one of three different resistances:R1 530, R2 535, or R3 540. Although not limited in this respect, typicalvalues may be 100Ω, 1KΩ, and 10 KΩ. A typical value for R4 565 may be50Ω which would be a desirable value for most RF detector designs.Assuming a high input impedance for the detector 555, the voltagecoupling levels would then be ⅓, 1/21, and 1/201.

This corresponds to voltage coupling levels of −9.5 dB, −26.4 dB, and−46 dB. At high power levels the lowest coupling is desired. At lowpower levels, the highest coupling level is desired. The dynamic rangeof the control loop is equal to that of the detector plus the differencein dB between the highest and lowest coupling levels. As an example,assume a simple diode detector is used which has about 25 dB of dynamicrange. The loop dynamic range will then be 25+[−9.5−(−46)]=61.6 dB. Theimprovement over using no variable voltage divider is more than 36 dB.

Equally important as enhancing the dynamic range is improving the outputharmonics and IP3 of the module. The variable voltage divider 550 willallow the detector input port 505 to be more isolated at the higherpower levels. This will improve linearity of the module for high signallevels.

Turning now to FIG. 6, generally at 600 are the functional blocks of avariable voltage divider 640, and the RF matching network 610 may becombined in hardware to some degree by understanding that the outputnode 625 of the matching network 610 may be connected to a shunt RFbranch comprised of a series string of capacitors 660 and to impedance635. An input node for RF_(in) 605 may also be connected to the RFmatching network 610. This series string 660 may be a RF voltage divider640, and by selectively tapping into various circuit nodes along thestring, one may obtain a variable output voltage divider 640. In anembodiment of the present invention, this is done with a digitallycontrolled RF switch 630. The switch 630 may be realized with FETs,MEMS, PIN diodes, or any other RF switch technology. Associated withvariable voltage divider 640 is RF voltage detector 655 and controller620, which is further connected to RF matching network 610 via biasvoltage driver circuit 615.

As a practical matter, the resistance of R1 645 will need to be muchhigher (>10×) than the reactance of the string of series capacitors 660between the tap point and ground. An alternative circuit to FIG. 6 wouldhave the resistor R₁ 645 moved to the capacitor side of the switch SW₁630 and placed in each of the three lines going to the tap points. Thiswill allow the resistors to be built on-chip with the tunable IC used inthe matching network. Resister R4 may also be utilized at 650.

Some embodiments of the invention may be implemented, for example, usinga machine-readable medium or article which may store an instruction or aset of instructions that, if executed by a machine, for example, by thesystem of FIG. 1 or FIG. 2, by controller 125 and 235 in communicationwith bias voltage driver circuit 120 and 230, by processor 355 of FIG.3, or by other suitable machines, cause the machine to perform a methodand/or operations in accordance with embodiments of the invention. Suchmachine may include, for example, any suitable processing platform,computing platform, computing device, processing device, computingsystem, processing system, computer, processor, or the like, and may beimplemented using any suitable combination of hardware and/or software.The machine-readable medium or article may include, for example, anysuitable type of memory unit, memory device, memory article, memorymedium, storage device, storage article, storage medium and/or storageunit, for example, memory, removable or non-removable media, erasable ornon-erasable media, writeable or re-writeable media, digital or analogmedia, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM),Compact Disk Recordable (CD-R), Compact Disk Re-Writeable (CD-RW),optical disk, magnetic media, various types of Digital Versatile Disks(DVDs), a tape, a cassette, or the like. The instructions may includeany suitable type of code, for example, source code, compiled code,interpreted code, executable code, static code, dynamic code, or thelike, and may be implemented using any suitable high-level, low-level,object-oriented, visual, compiled and/or interpreted programminglanguage, e.g., C, C++, Java, BASIC, Pascal, Fortran, Cobol, assemblylanguage, machine code, or the like.

An embodiment of the present invention provides a machine-accessiblemedium that provides instructions, which when accessed, cause a machineto perform operations comprising adapting an RF matching network tomaximize RF power transferred from at least one RF input port to atleast one RF output port by controlling the variation of the voltage orcurrent to voltage or current controlled variable reactive elements insaid RF matching network to maximize the RF voltage at said at least oneRF output port. The machine-accessible medium of the present inventionmay further comprise said instructions causing said machine to performoperations further comprising receiving information from a voltagedetector connected to said at least one RF output port which determinesthe voltage at said at least one RF output port and providing voltageinformation to a controller that controls a bias driving circuit whichprovides voltage or current bias to said RF matching network.

Some embodiments of the present invention may be implemented bysoftware, by hardware, or by any combination of software and/or hardwareas may be suitable for specific applications or in accordance withspecific design requirements. Embodiments of the invention may includeunits and/or sub-units, which may be separate of each other or combinedtogether, in whole or in part, and may be implemented using specific,multi-purpose or general processors or controllers, or devices as areknown in the art. Some embodiments of the invention may include buffers,registers, stacks, storage units and/or memory units, for temporary orlong-term storage of data or in order to facilitate the operation of aspecific embodiment.

Throughout the aforementioned description, BST may be used as a tunabledielectric material that may be used in a tunable dielectric capacitorof the present invention. However, the assignee of the presentinvention, Paratek Microwave, Inc. has developed and continues todevelop tunable dielectric materials that may be utilized in embodimentsof the present invention and thus the present invention is not limitedto using BST material. This family of tunable dielectric materials maybe referred to as Parascan®.

The term Parascan® as used herein is a trademarked term indicating atunable dielectric material developed by the assignee of the presentinvention. Parascan® tunable dielectric materials have been described inseveral patents. Barium strontium titanate (BaTiO3-SrTiO3), alsoreferred to as BSTO, is used for its high dielectric constant(200-6,000) and large change in dielectric constant with applied voltage(25-75 percent with a field of 2 Volts/micron). Tunable dielectricmaterials including barium strontium titanate are disclosed in U.S. Pat.No. 5,312,790 to Sengupta, et al. entitled “Ceramic FerroelectricMaterial”; U.S. Pat. No. 5,427,988 by Sengupta, et al. entitled “CeramicFerroelectric Composite Material-BSTO-MgO”; U.S. Pat. No. 5,486,491 toSengupta, et al. entitled “Ceramic Ferroelectric CompositeMaterial-BSTO-ZrO2”; U.S. Pat. No. 5,635,434 by Sengupta, et al.entitled “Ceramic Ferroelectric Composite Material-BSTO-Magnesium BasedCompound”; U.S. Pat. No. 5,830,591 by Sengupta, et al. entitled“Multilayered Ferroelectric Composite Waveguides”; U.S. Pat. No.5,846,893 by Sengupta, et al. entitled “Thin Film FerroelectricComposites and Method of Making”; U.S. Pat. No. 5,766,697 by Sengupta,et al. entitled “Method of Making Thin Film Composites”; U.S. Pat. No.5,693,429 by Sengupta, et al. entitled “Electronically Graded MultilayerFerroelectric Composites”; U.S. Pat. No. 5,635,433 by Sengupta entitled“Ceramic Ferroelectric Composite Material BSTO-ZnO”; U.S. Pat. No.6,074,971 by Chiu et al. entitled “Ceramic Ferroelectric CompositeMaterials with Enhanced Electronic Properties BSTO Mg BasedCompound-Rare Earth Oxide”. These patents are incorporated herein byreference. The materials shown in these patents, especially BSTO-MgOcomposites, show low dielectric loss and high tunability. Tunability isdefined as the fractional change in the dielectric constant with appliedvoltage.

Barium strontium titanate of the formula Ba_(x)Sr_(1-x)TiO₃ is apreferred electronically tunable dielectric material due to itsfavorable tuning characteristics, low Curie temperatures and lowmicrowave loss properties. In the formula Ba_(x)Sr_(1-x)TiO₃, x can beany value from 0 to 1, preferably from about 0.15 to about 0.6. Morepreferably, x is from 0.3 to 0.6.

Other electronically tunable dielectric materials may be used partiallyor entirely in place of barium strontium titanate. An example isBa_(x)Ca_(1-x)TiO₃, where x is in a range from about 0.2 to about 0.8,preferably from about 0.4 to about 0.6. Additional electronicallytunable ferroelectrics include Pb_(x)Zr_(1-x)TiO₃ (PZT) where x rangesfrom about 0.0 to about 1.0, Pb_(x)Zr_(1-x)SrTiO₃ where x ranges fromabout 0.05 to about 0.4, KTa_(x)Nb_(1-x)O₃ where x ranges from about 0.0to about 1.0, lead lanthanum zirconium titanate (PLZT), PbTiO₃,BaCaZrTiO₃, NaNO₃, KNbO₃, LiNbO₃, LiTaO₃, PbNb₂O₆, PbTa₂O₆, KSr(NbO₃)and NaBa₂(NbO₃)5KH₂PO₄, and mixtures and compositions thereof. Also,these materials can be combined with low loss dielectric materials, suchas magnesium oxide (MgO), aluminum oxide (Al₂O₃), and zirconium oxide(ZrO₂), and/or with additional doping elements, such as manganese (MN),iron (Fe), and tungsten (W), or with other alkali earth metal oxides(i.e. calcium oxide, etc.), transition metal oxides, silicates,niobates, tantalates, aluminates, zirconnates, and titanates to furtherreduce the dielectric loss.

In addition, the following U.S. patents and patent Applications,assigned to the assignee of this application, disclose additionalexamples of tunable dielectric materials: U.S. Pat. No. 6,514,895,entitled “Electronically Tunable Ceramic Materials Including TunableDielectric and Metal Silicate Phases”; U.S. Pat. No. 6,774,077, entitled“Electronically Tunable, Low-Loss Ceramic Materials Including a TunableDielectric Phase and Multiple Metal Oxide Phases”; U.S. Pat. No.6,737,179 filed Jun. 15, 2001, entitled “Electronically TunableDielectric Composite Thick Films And Methods Of Making Same; U.S. Pat.No. 6,617,062 entitled “Strain-Relieved Tunable Dielectric Thin Films”;U.S. Pat. No. 6,905,989, filed May 31, 2002, entitled “TunableDielectric Compositions Including Low Loss Glass”; U.S. patentapplication Ser. No. 10/991,924, filed Nov. 18, 2004, entitled “TunableLow Loss Material Compositions and Methods of Manufacture and UseTherefore” These patents and patent applications are incorporated hereinby reference.

The tunable dielectric materials can also be combined with one or morenon-tunable dielectric materials. The non-tunable phase(s) may includeMgO, MgAl₂O₄, MgTiO₃, Mg₂SiO₄, CaSiO₃, MgSrZrTiO₆, CaTiO₃, Al₂O₃, Sio₂and/or other metal silicates such as BaSiO₃ and SrSiO₃. The non-tunabledielectric phases may be any combination of the above, e.g., MgOcombined with MgTiO₃, MgO combined with MgSrZrTiO₆, MgO combined withMg₂SiO₄, MgO combined with Mg₂SiO₄, Mg₂SiO₄ combined with CaTiO₃ and thelike.

Additional minor additives in amounts of from about 0.1 to about 5weight percent can be added to the composites to additionally improvethe electronic properties of the films. These minor additives includeoxides such as zirconnates, tannates, rare earths, niobates andtantalates. For example, the minor additives may include CaZrO₃, BaZrO₃,SrZrO₃, BaSnO₃, CaSnO₃, MgSnO₃, Bi2O₃/2SnO₂, Nd₂O₃, Pr₇O₁₁, Yb₂O₃,H_(o2)O₃, La₂O₃, MgNb₂O₆, SrNb₂O₆, BaNb₂O₆, MgTa₂O₆, BaTa₂O₆ and Ta₂O₃.

Films of tunable dielectric composites may comprise Ba1-xSrxTiO3, wherex is from 0.3 to 0.7 in combination with at least one non-tunabledielectric phase selected from MgO, MgTiO₃, MgZrO₃, MgSrZrTiO₆, Mg₂SiO₄,CaSiO₃, MgAl₂O₄, CaTiO₃, Al₂O₃, SiO₂, BaSiO₃ and SrSiO₃. Thesecompositions can be BSTO and one of these components, or two or more ofthese components in quantities from 0.25 weight percent to 80 weightpercent with BSTO weight ratios of 99.75 weight percent to 20 weightpercent.

The electronically tunable materials may also include at least one metalsilicate phase. The metal silicates may include metals from Group 2A ofthe Periodic Table, i.e., Be, Mg, Ca, Sr, Ba and Ra, preferably Mg, Ca,Sr and Ba. Preferred metal silicates include Mg₂SiO₄, CaSiO₃, BaSiO₃ andSrSiO₃. In addition to Group 2A metals, the present metal silicates mayinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. For example, such metal silicates may include sodiumsilicates such as Na₂SiO₃ and NaSiO₃-5H₂O, and lithium-containingsilicates such as LiAlSiO₄, Li2SiO₃ and Li₄SiO₄. Metals from Groups 3A,4A and some transition metals of the Periodic Table may also be suitableconstituents of the metal silicate phase. Additional metal silicates mayinclude Al₂Si₂O₇, ZrSiO₄, KalSi₃O₈, NaAlSi₃O₈, CaAl₂Si₂O₈, CaMgSi₂O₆,BaTiSi₃O₉ and Zn₂SiO₄. The above tunable materials can be tuned at roomtemperature by controlling an electric field that is applied across thematerials.

In addition to the electronically tunable dielectric phase, theelectronically tunable materials can include at least two additionalmetal oxide phases. The additional metal oxides may include metals fromGroup 2A of the Periodic Table, i.e., Mg, Ca, Sr, Ba, Be and Ra,preferably Mg, Ca, Sr and Ba. The additional metal oxides may alsoinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. Metals from other Groups of the Periodic Table may also besuitable constituents of the metal oxide phases. For example, refractorymetals such as Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta and W may be used.Furthermore, metals such as Al, Si, Sn, Pb and Bi may be used. Inaddition, the metal oxide phases may comprise rare earth metals such asSc, Y, La, Ce, Pr, Nd and the like.

The additional metal oxides may include, for example, zirconnates,silicates, titanates, aluminates, stannates, niobates, tantalates andrare earth oxides. Preferred additional metal oxides include Mg₂SiO₄,MgO, CaTiO₃, MgZrSrTiO₆, MgTiO₃, MgA₁₂O₄, WO3, SnTiO₄, ZrTiO₄, CaSiO₃,CaSnO₃, CaWO₄, CaZrO₃, MgTa₂O₆, MgZrO₃, MnO₂, PbO, Bi₂O₃ and La₂O₃.Particularly preferred additional metal oxides include Mg₂SiO₄, MgO,CaTiO₃, MgZrSrTiO₆, MgTiO₃, MgAl₂O₄, MgTa₂O₆ and MgZrO₃.

The additional metal oxide phases are typically present in total amountsof from about 1 to about 80 weight percent of the material, preferablyfrom about 3 to about 65 weight percent, and more preferably from about5 to about 60 weight percent. In one preferred embodiment, theadditional metal oxides comprise from about 10 to about 50 total weightpercent of the material. The individual amount of each additional metaloxide may be adjusted to provide the desired properties. Where twoadditional metal oxides are used, their weight ratios may vary, forexample, from about 1:100 to about 100:1, typically from about 1:10 toabout 10:1 or from about 1:5 to about 5:1. Although metal oxides intotal amounts of from 1 to 80 weight percent are typically used, smalleradditive amounts of from 0.01 to 1 weight percent may be used for someapplications.

The additional metal oxide phases can include at least two Mg-containingcompounds. In addition to the multiple Mg-containing compounds, thematerial may optionally include Mg-free compounds, for example, oxidesof metals selected from Si, Ca, Zr, Ti, Al and/or rare earths.

While the present invention has been described in terms of what are atpresent believed to be its preferred embodiments, those skilled in theart will recognize that various modifications to the discloseembodiments can be made without departing from the scope of theinvention as defined by the following claims.

1. An apparatus, comprising: an RF matching network connected to atleast one RF input port and at least one RF output port and includingone or more voltage or current controlled variable reactive elements; avoltage detector connected to said at least one RF output port via avariable voltage divider to determine the voltage at said at least oneRF output port and provide voltage information to a controller thatcontrols a bias driving circuit which provides voltage or current biasto said RF matching network; a variable voltage divider connected tosaid voltage detector and implemented using a multi-pole RF switch toselect one of a plurality of different resistance ratios to improve thedynamic range of said apparatus; and wherein said RF matching network isadapted to maximize RF power transferred from said at least one RF inputport to said at least one RF output port by varying the voltage orcurrent to said voltage or current controlled variable reactive elementsto maximize the RF voltage at said at least one RF output port.
 2. Theapparatus of claim 1, wherein said voltage detector is a diode detectorand wherein said variable voltage divider connected to said voltagedetector is adapted to improve the dynamic range of said apparatus. 3.The apparatus of claim 2, further comprising a loop controllerassociated with said variable voltage divider to make said variablevoltage divider programmable.
 4. The apparatus of claim 1, wherein saidvariable voltage divider is operable to allow a detector at said outputport to be more isolated at higher power levels and improve linearity ofthe module for high signal levels.
 5. The apparatus of claim 1, whereinsaid RF output node is connected to a shunt RF branch comprising aseries string of capacitors.
 6. The apparatus of claim 5, wherein byselectively tapping into various circuit nodes along said string, avariable output voltage divider is obtained.
 7. The apparatus of claim6, wherein tapping into various circuit nodes is accomplished by adigitally controlled RF switch.
 8. The apparatus of claim 7, whereinsaid RF switch is selected from the group consisting of: FETs, MEMS orPIN diodes.
 9. The apparatus of claim 7, further comprising a resistorplaced on the capacitor side of said RF switch and thereby allow saidresistor to be built on-chip.
 10. A method of adaptive impedancematching, comprising: connecting an RF matching network to at least oneRF input port and at least one RF output port and including one or morevoltage or current controlled variable reactive elements; using avoltage detector connected to said at least one RF output port via avariable voltage divider, implemented by using a multi-pole RF switch toselect one of plurality of different resistance ratios, to determine thevoltage at said at least one RF output port and providing said voltageinformation to a controller that controls a bias driving circuit whichprovides voltage or current bias to said RF matching network; andadapting said RF matching network to maximize RF power transferred fromsaid at least one RF input port to said at least one RF output port byvarying the voltage or current to said voltage or current controlledvariable reactive elements to maximize the RF voltage at said at leastone RF output port.
 11. The method of claim 10, wherein said voltagedetector is a diode detector and wherein said variable voltage dividerconnected to said voltage detector is adapted to improve the dynamicrange of said apparatus.
 12. The method of claim 10, further comprisingassociating a loop controller with said variable voltage divider to makesaid variable voltage divider programmable.
 13. The method of claim 10,further comprising connecting said RF output node to a shunt RF branchcomprising a series string of capacitors.
 14. The method of claim 13,further comprising selectively tapping into various circuit nodes alongsaid string.
 15. The method of claim 16, further comprising using adigitally controlled RF switch to tap into various circuit nodes. 16.The method of claim 15, further comprising placing a resistor on thecapacitor side of said RF switch and in each line going to tap points ofsaid capacitors thereby allowing said resistor to be built on-chip.